SEMICONDUCTOR LIGHT EMITTING DEVICE INCLUDING GaAs SUBSTRATE

ABSTRACT

A semiconductor light emitting device including: a substrate made of GaAs; and a semiconductor layer formed on the substrate, in which part of the substrate on a side opposite to the semiconductor layer is removed by etching so that the semiconductor light emitting device has a thickness of not more than 60 μm.

CROSS REFERENCE TO RELATED APPLICATOINS AND INCORPORATION BY REFERENCE

This is a Continuation of U.S. application Ser. No. 12/007,005, filed onJan. 4, 2008, and allowed on Nov. 1, 2013, the subject matter of whichis incorporated herein by reference.

The parent application Ser. No. 12/007,005 is based upon and claims thebenefit of priority from prior Japanese Patent Application P2007-000586filed on Jan. 5, 2007 and prior Japanese Patent Application P2007-033418filed on Feb. 14, 2007; the entire contents of which are incorporated byreference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor light emitting devicemanufactured by growing semiconductor layers on a GaAs substrate and amethod for manufacturing the same.

2. Description of the Related Art

A semiconductor light emitting device in which semiconductor layersincluding a light emitting layer composed of an InGaAlP layer or thelike are stacked on a GaAs substrate is hitherto known. However, theconventional light emitting device has a problem that the output lightemitted to the outside is small because the GaAs substrate absorbs lightemitted by she light emitting layer. To solve the problem, there is aknown technique of removing the substrate by abrasion. However, removingthe substrate by abrasion causes another problem of cracks occurring inthe semiconductor light emitting device cracks. Therefore, there is adisclosure of a technique to solve such a problem of cracks of thesemiconductor light emitting device occurring at removal of thesubstrate.

For example, Japanese Patent Laid-open Publication No. 1999-168236(Patent Literature 1) discloses a semiconductor light emitting devicemanufactured by growing semiconductor layers including a light emittinglayer composed of an InGaAlP layer on a GaAs layer. In thissemiconductor light emitting device, after the semiconductor layers aregrown on the substrate, an alternate supporting member composed of aflexible and conductive film is attached to the semiconductor layer. Thesubstrate is then removed by etching, and a metallic electrode is formedon a surface of the InGaAlP layer from which she substrate is removed tomanufacture the semiconductor device.

As described above, in the semiconductor light emitting device of PatentLiterature 1, the removal of the substrate reduces the absorption oflight emitted from the light emitting layer, thus increasing the outputlight emitted to the outside.

However, the semiconductor light emitting device of Patent Literature 1has a difficulty in forming an ohmic contact between the metallicelectrode and semiconductor layers because the GaAs substrate is removedand the metallic electrode is formed on the InGaAlP layer exposed b theremoval of the GaAs substrate.

SUMMARY OF THE INVENTION

A semiconductor light emitting device according to the present inventionincludes: a substrate made of GaAs; and a semiconductor layer formed onthe substrate. Part of the substrate on a side opposite to thesemiconductor layer is removed by etching so that the semiconductorlight emitting device has a thickness of not more than 60 μm.

A method for manufacturing a semiconductor light emitting deviceaccording to the present invention includes: a growing step of growing asemiconductor layer on a substrate made of GaAs; an attachment step ofattaching a temporary supporting substrate to a surface of thesemiconductor layer opposite to the substrate with an adhesive made ofpolyimide system resin; and an etching step of removing part of thesubstrate on a side opposite to the semiconductor layer by etching sothat the semiconductor light emitting device has a thickness of not morethan 60 μm in a stacking direction.

According to the semiconductor light emitting device of the presentinvention and method for manufacturing the same, the removal of the partof the substrate made of GaAs reduces absorption of light and increasesthe heat radiation. Moreover, the remaining part of the substrate madeof GaAs, which easily forms an ohmic contact to a metallic electrode,facilitates forming an ohmic contact of the electrode compared to thecase where the substrate is entirely removed.

Moreover, since the part of the substrate is removed so that thesemiconductor device has a thickness of about 60 μm in the stackingdirection, even when the semiconductor light emitting device is coveredwith a protection film of resin or the like into a semiconductor lightemitting apparatus, the semiconductor light emitting apparatus can beconfigured to have a thickness of not more than about 200 μm andtherefore used in various applications.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view or a semiconductor light emittingdevice according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the semiconductor light emittingdevice at a step of a manufacturing process.

FIG. 3 is a cross-sectional view of the semiconductor light emittingdevice at another step of the manufacturing process.

FIG. 4 is a cross-sectional view of the semiconductor light emittingdevice at still another step of the manufacturing process.

FIG. 5 is a cross-sectional view of the semiconductor light emittingdevice at still another step of a manufacturing process.

FIG. 6 is a cross-sectional view of the semiconductor light emittingdevice at still another step of the manufacturing process.

FIG. 7 is a cross-sectional view of the semiconductor light emittingdevice at a still another step of the manufacturing process.

FIG. 8 is a cross-sectional view of a semiconductor light emittingdevice according to a second embodiment of the present invention.

FIG. 9 is a cross-sectional view of a semiconductor light emittingdevice according to a modification of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Various embodiments of the present invention will be described withreference to the accompanying drawings. It is to be noted that the sameor similar reference numerals are applied to the same or similar partsand elements throughout the drawings, and the description of the same orsimilar parts and elements will be omitted or simplified.

With reference to the drawings, a description is given of a firstembodiment of the present invention. FIG. 1 is a cross-sectional view ofa semiconductor light emitting device according to a first embodiment ofthe present invention.

As shown in FIG. 1, a semiconductor light emitting device 1 includes asubstrate 2, a substrate-side reflecting layer 3 formed on the substrate2, an n-type clad layer 4, a light emitting layer 5, p-type clad layer6, a p-type contact layer 7, and an electrode-side reflecting layer 8.The semiconductor light emitting device 1 further includes a pair of ap-side electrode 9 and an n-side electrode 10. The semiconductor lightemitting device 1 is configured to have a thickness of not more thanabout 60 μm in a stacking direction.

The substrate 2 is made of n-type GaAs. The substrate 2 is etched to athickness of about 1 μm in the stacking direction (a direction indicatedby an arrow A-B) so that the total thickness of the semiconductor lightemitting device 1 in the stacking direction is not more than about 60μm.

The substrate-side reflecting layer 3 includes first and secondreflecting layers 3 a and 3 b.

The first reflecting layer 3 a is to increase a light reflectionbandwidth. Increasing the light reflection bandwidth means increasingincident angle of light rays which can be reflected. The firstreflecting layer 3 a has a Distributed Bragg Reflector (DBR) structurein which 10 pairs of about 40 nm thick n-type Al_(y)In_(1-y)P layers(0.3<=y<=0.7) and about 40 nm thick n-type GaAs layers are stacked oneach other. The n-type Al_(y)In_(1-y)P and n-type GaAs layers are dopedwith silicon as an n-type dopant.

The second reflecting layer 3 b is to increase reflected lightintensity. The second reflecting layer 3 b has a DBR structure in which10 pairs of alternating about 40 nm thick n-type Al_(y)In_(1-y)P layers(0.3<=y<=0.7) and about 40 nm thick n-type(Al_(x)Ga_(1-x))_(0.5)In_(0.5)P layers (0.3<=x<=0.85) are stacked oneach other. The n-type Al_(y)In_(1-y)P and n-type(Al_(x)Ga_(1-x))_(0.5)In_(0.5)P layers are doped with silicon as ann-type dopant.

The n-type clad layer 4 is composed of an about 1 μm thick n-typeAl_(y)In_(1-y)P layer (0.3<=y<=0.7) doped with selenium as an n-typedopant.

The light emitting layer 5 emits light with a wavelength of about 540 to650 nm. The light emitting layer 5 has a multi-quantum well structure inwhich 60 pairs of alternating well layers each composed of an(Al_(p)Ga_(1-p))_(q)In_(1-q)P layer (0<=p<=0.5, 0.3<=q<=0.7) with athickness of about 2 to 20 nm and barrier layers each composed of(Al_(r)Ga_(1-r))_(s)In_(1-s)P layers (0<=r<=1, 0.3<=s<=0.7) with athickness of about 3 to 30 nm are stacked on each other.

The p-type clad layer 6 is composed of an about 1 μm thick p-typeAl_(0.5)In_(0.5)P layer doped with zinc as a p-type dopant.

The p-type contact layer 7 is composed of an about 20 to 40 μm thickp-type GaP layer doped with zinc as a p-type dopant.

The electrode-side reflecting layer 8 has a DBR structure in which 5 to10 pairs of alternating about 40 nm thick p-type Al_(y)In_(1-y)P layers(0.3<=y<=0.7) doped with zinc as a p-type dopant and p-type(Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P layers are stacked on each other. Theelectrode-side reflecting layer 8 has a circular shape in a plan viewand is formed on a part of the p-type contact layer 7.

The p-side electrode 9 forms an ohmic contact to the p-type contactlayer 7 and electrode-side reflecting layer 8. The p-side electrode 9has a stacking structure of AuBe/Au with a thickness of about 3000 nm.The material of the p-side electrode 9 can be AuZn instead of AuBe. Asshown in FIG. 1, the p-side electrode 9 has a square U-shape opendownward in a side cross-sectional view and a circular shape with adiameter larger than that of the electrode-side reflecting layer 8 in aplan view. In other words, the p-side electrode 9 covers upper and sidesurfaces of the electrode-side reflecting layer 8, and a part of abottom surface of the p-side electrode 9 is in contact with the p-typecontact layer 7.

The n-side electrode 10 forms an ohmic contact to a rear surface of thesubstrate 2. The n-side electrode 10 has a stacking structure of AuGe/Auwith a thickness of about 1000 nm.

Next, a description is given of an operation of the aforementionedsemiconductor light emitting device.

When the semiconductor light emitting device 1 is supplied with currentthrough the p-side and n-side electrodes 9 and 10, first, holes aresupplied from the p-side electrode 9, and electrons are supplied fromthe n-side electrode 10. Herein, most of the holes supplied from thep-side electrode 10 are injected not through the electrode-sidereflecting layer 8 but directly into the p-type contact layer 7 and theninjected through the p-type clad layer 6 into the light emitting layer5. The electrons are injected through the substrate-side reflectinglayer 3 and n-type clad layer 4 into the light emitting layer 5. Theholes and electrons injected into the light emitting layer 5 arerecombined to each other to emit light with a wavelength of about 540 to650 nm.

Herein, light rays traveling in the direction A are transmitted throughthe p-type clad layer 6 and p-type contact layer 7 to reach the uppersurface of the p-type contact layer 7. Among the light rays which havereached the upper surface of the p-type contact layer, light rays whichhave reached an area other than the electrode-side reflecting layer 8are radiated to the outside while light rays which have reached theelectrode-side reflecting layer 8 are reflected on the electrode-sidereflecting layer 8 to travel in the direction B without being absorbedby the p-side electrode 9.

Among the light rays traveling in the direction B, most of light rayshaving small incident angles are reflected on the second reflectinglayer 3. However, light rays with large incident angles are notreflected on the second reflecting layer 3 and transmitted through thesecond reflecting layer 3 b to be incident on the first reflecting layer3 a. Herein, the incident angle of light rays which can be reflected bythe first reflecting layer 3 a is larger than that of the secondreflecting layer 3 b. Accordingly, even light rays which have largeincident angle and cannot be reflected on the second reflecting layer 3b can be reflected by the first reflecting layer 3 a. The light raysreflected on the second and first reflecting layers 3 b and 3 a travelin the direction A to be transmitted through the layers from the n-typeclad layer 4 to the p-type contact layer 7 and radiated to the outside.

In the semiconductor light emitting device 1, the GaAs substrate 2 ispartially removed so as to have a thickness of about 1 μm. Theabsorption of light emitted by the light emitting layer 5 is thereforereduced to increase the output light emitted to the outside. Moreover,heat radiation is increased, and it is therefore possible to prevent ashift of wavelength of emitted light due to an increase in temperatureof the semiconductor light emitting device 1. As the heat radiationincreases, light emission intensity of the semiconductor light emittingdevice 1 increases.

Next, a description is given of a method for manufacturing theaforementioned semiconductor light emitting device. FIGS. 2 to 7 arecross-sectional views of the semiconductor light emitting device atrespective manufacturing steps.

First, the substrate 2 of n-type GaAs is put in an MOCVD apparatus.Temperature of the substrate 2 is set to about 600 to 800° C.,preferably about 700° C.

Next, as shown in FIG. 2, trimethylaluminum (hereinafter, TMA),trimethylindium (hereinafter, TMI), phosphine, and monosilane aresupplied with carrier gas (H₂ gas) to the MOCVD apparatus to form anabout 40 nm thick n-type Al_(y)In_(1-y)P layer doped with silicon.Trimethylgallium (hereinafter, TMG), arusine, and monosilane aresupplied to form an about 10 nm thick n-type GaAs layer doped withsilicon. Such a process is repeated to stack 10 pairs of alternatingn-type Al_(y)In_(1-y)P and n-type GaAs layers, thus forming the firstreflecting layer 3 a.

Next, TMA, TMI, phosphine, and monosilane are supplied with the carriergas to form an about 40 nm thick n-type Al_(y)In_(1-y)P layer doped withsilicon. Thereafter, TMA, TMG, TMI, phosphine, and monosilane aresupplied to form an about 40 nm thick n-type(Al_(x)GA_(1-x))_(0.5)In_(0.5)P layer. Such a process is repeated tostack 10 pairs of alternating n-type Al_(y)In_(1-y)P and(Al_(x)GA_(1-x))_(0.5)In_(0.5)P layers, thus forming the secondreflecting layer 3 b.

Next, TMA, TMI, phosphine, and hydrogen selenide are supplied with thecarrier gas to form the n-type clad layer 4 composed of an about 1 μmthick n-type Al_(y)In_(1-y)P layer doped with selenium.

Next, TMI, TMG, and phosphine are supplied with the carrier gas to formthe well layer composed of an (Al_(p)Ga_(1-p))_(q)In_(1-q)P layer havinga thickness of about 2 to 20 nm. Thereafter, TMA, TMG, TMI, andphosphine are supplied to form the barrier layer composed of an(Al_(r)Ga_(1-r))_(s)In_(1-s)P layer having a thickness of about 3 to 30nm. Such a process is repeated to stack 60 pairs of alternating well andbarrier layers are stacked, thus forming the light emitting layer 5.

Next, TMA, TMI, phosphine, and dimethylzinc are supplied with thecarrier gas to form the p-type clad layer 6 composed of an about 1 μmthick p-type Al_(0.5)In_(0.5)P layer doped with zinc.

Next, TMG, phosphine, and dimethylzinc are supplied with the carrier gasto form the p-type contact layer 7 composed of an about 20 to 40 μmthick p-type GaP layer doped with zinc.

Next, TMA, TMI, phosphine, and dimethyl zinc are supplied to form anabout 40 nm thick p-type Al_(y)In_(1-y)P layer doped with zinc.Thereafter, TMA, TMG, TMI, phosphine, and dimethylzinc are supplied toform an about 40 nm thick p-type (Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P layerdoped with zinc. Such a process is repeated to stack 5 to 10 pairs ofalternating p-type Al_(y)In_(1-y)P and p-type(Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P layers, thus forming a DBR structure.The DBR structure is then patterned by photolithography and etching toform the electrode-side reflecting layer 8.

Next, an about 3000 nm thick stacking structure of AuBe (or AuZn)/Au isformed by spattering so as to cover the upper surface of the p-typecontact layer 7 and the upper and side surfaces of the electrode-sidereflecting layer 8. The stacking structure is then patterned usingphotolithography and etching to form the p-side electrodes 9.

Next, as shown in FIG. 3, an adhesive 21 composed of polyimide systemresin is applied by spin coating to entire exposed surfaces of thep-type contact layer 7 and p-side electrodes 9 and then heated at about115° C. for about 5 minutes to evaporate the solvent. Herein, an exampleof polyimide system resin used for the adhesive 21 can be a mixture ofabout 70% to 95% 1-methyl-2pyrrolidinone (NMP) and about 5 to 30%polyamic acid resin.

Next, as shown in FIG. 4, on the adhesive 21, a temporary supportingsubstrate 22 which is made of quartz or sapphire and includes theplurality of holes 22 a formed is placed and then heated at about 115°C. for about 5 minutes so as to be attached to the p-type contact layer7 and p-side electrodes 9 (a surface opposite to the substrate 2)through the adhesive 21.

Next, as shown in FIG. 5, using an acid etching solution of a mixture ofH₃PO₄, H₂O₂, and H₂O in a ratio of 1/1/3, the substrate 2 is etched tobe removed. Herein, the substrate 2 is not entirely removed by etchingand partially removed to have a thickness of about 1 μm so that a totalthickness of the semiconductor light emitting device 1 in the stackingdirection is not more than about 60 μm.

Next, as shown in FIG. 6, in a state where the temporary supportingsubstrate 22 is attached, the n-side electrode 10 composed of an about1000 nm thick stacking structure of AuGe/Au formed on the entire lowersurface of the substrate 2. Thereafter, annealing is performed to fromohmic contacts between the p-side electrodes 9 and p-type contact layer7 and the n-side electrode 10 and substrate 2.

Next, as shown in FIG. 7, the adhesive 21 composed of polyimide systemresin is dissolved using an alkali solution with a concentration ofabout 1% such as a KOH aqueous solution to separate the temporarysupporting substrate 22. Herein, the alkali solution enters not onlythrough the periphery of the temporary supporting substrate 22 but alsothrough the plurality of holes 22 a to dissolve the adhesive 21.

The thus-obtained product is eventually divided into device units, thuscompleting the semiconductor light emitting device 1.

As described above, in the semiconductor light emitting device 1, theGaAs substrate 2 is not entirely removed by etching and is etched so asto have a thickness of about 1 μm. Accordingly, it is possible to moreeasily form an ohmic contact between the n-side electrode 10 andsemiconductor layers than the case where the substrate is entirelyremoved.

Moreover, since part of the substrate 2 is removed so that thesemiconductor device 1 has a thickness of about 60 μm in the stackingdirection, even when the semiconductor light emitting device 1 iscovered with a protection film of resin or the like into a semiconductorlight emitting apparatus, the semiconductor light emitting apparatus canbe configured to have a thickness of not more than about 200 μm andtherefore used in various applications.

Furthermore, use of the adhesive 21 made of polyimide system resin forattachment of the temporary supporting substrate 22 can provide thefollowing effects. First, since polyimide system resin constituting theadhesive 21 is highly resistant to acid, the adhesive 21 is preventedfrom being dissolved by the acid etching solution used in etching thesubstrate 2. Secondly, since the polyimide system resin constituting theadhesive 21 is highly resistant to heat, the annealing to form ohmiccontacts of the electrodes 9 and 10 can be performed even with thetemporary supporting substrate 22 attached. Thirdly, since the polyimidesystem resin constituting the adhesive 21 easily dissolves in alkalisolution, the adhesive 21 can be easily dissolved by the alkali solutionsuch as KOH solution for separating the temporary supporting substrate2.

Moreover, since the n-side electrode 10 is formed and annealing to forman ohmic contact is performed in a state where the temporary supportingsubstrate 22 is attached, cracks of the semiconductor light emittingdevice 1 can be prevented.

Furthermore, since the temporary supporting substrate 22 provided withthe plurality of holes 22 is used, the alkali solution to dissolve theadhesive 21 can be injected through the individual holes 22 a, and theadhesive 21 can be quickly dissolved.

Next, with reference to the drawing, a description is given of a secondembodiment obtained by partially modifying the aforementioned firstembodiment. FIG. 8 is a cross-sectional view of a semiconductor lightemitting device according to the second embodiment. Same components asthose of the first embodiment are given same reference numerals, and adescription thereof is omitted.

As shown in FIG. 8, a semiconductor light emitting device 1A includes asubstrate 2 a made of n-type GaAs doped with silicon, a substrate-sidereflecting layer 3A laid on the substrate 2 a, a first n-type clad layer4 a, a second n-type clad layer 4 b, a light emitting layer 5 a, a firstp-type clad layer 6 a, a second p-type clad layer 6 b, and a p-typecontact layer 7 a. The semiconductor light emitting device 1A furtherincludes a p-side electrode 9 a and an n-side electrode 10.

The semiconductor light emitting device 1A has a square shape of about100 μm×about 100 μm in a plan view. The semiconductor light emittingdevice 1A is configured to have a thickness of not more than 60 μm(preferably, not more than 40 μm) in the stacking direction.

The substrate-side reflecting layer 3A includes a first reflecting layer3 c and a second reflecting layer 3 d.

The first reflecting layer 3 c has an about 870 nm thick DBR structurein which 10 pairs of alternating about 45 nm thick n-type AlInP layersand about 42 nm thick n-type GaAs layers are stacked on each other. Then-type AlInP and n-type GaAs layers are doped with silicon as an n-typedopant.

The second reflecting layer 3 d has an 900 nm thick DBR structure inwhich 10 pairs of alternating about 45 nm thick n-type AlInP layers andabout 45 nm thick n-type Al_(0.3)Ga_(0.7)InP layers are stacked on eachother. The n-type AlInP and n-type Al_(0.3)Ga_(0.7)InP layers are dopedwith selenium as an n-type dopant.

The first n-type clad layer 4 a is composed of an about 800 nm thickn-type Al_(0.7)Ga_(0.3)InP layer doped with selenium as an n-typedopant. The second n-type clad layer 4 b is composed of an about 100 nmthick n-type AlInP layer doped with selenium as an n-type dopant.

The light emitting layer 5 a has an about 1080 nm thick MQW structure inwhich 65 pairs of alternating well layers each composed of an about 4.5nm thick GaInP layer and barrier layers each composed of an about 12 nmthick AlGaInP layer are stacked on each other. Between the lightemitting layer 5 a and second n-type clad layer 4 b, an n-type guidelayer (not shown) composed of an about 100 nm thick n-type AlGaInP layeris formed. Between the light emitting layer 5 a and first p-type cladlayer 6 a, a p-type guide layer (not shown) composed of an about 100 nmthick p-type AlGaInP layer is formed.

The first p-type clad layer 6 a is composed of an about 450 nmAl_(0.85)Ga_(0.15)InP layer doped with zinc as a p-type dopant. Thesecond p-type clad layer 6 b is composed of an about 450 nm thick AlInPlayer doped with zinc as a p-type dopant.

The p-type contact layer 7 a has a thickness of D₁ μm (2<=D₁<=10) and iscomposed of a p-type GaP layer doped with zinc as a p-type dopant.

The p-side electrode 9 a is formed on a part of an upper surface of thep-type contact layer 7 a so as to form an ohmic contact to the same. Thep-side electrode 9 a has a stacking structure of AuBe/Au with athickness of about 3000 nm. The material of the p-side electrode 9 a canbe AuZn instead of AuBe.

The semiconductor light emitting device 1A according to the secondembodiment has a total thickness of about 8.55 μm except the substrate 2a and p-type contact layer 7 a. To make the total thickness of thesemiconductor light emitting device 1A not more than 60 μm, part of thesubstrate 2 a is removed by etching in the stacking direction so that D₂satisfies the following equation:

D ₂=80−8.55−D ₁=51.45−D ₁ [μm]

where D₂ is a thickness of the substrate 2 a.

As described above, the semiconductor light emitting device 1A accordingto the second embodiment, in which part of the substrate 2 a is removedby etching in the stacking direction so that the total thickness of thedevice in the stacking direction is not more than 60 μm, has the sameeffects as those of the semiconductor light emitting device 1 of thefirst embodiment.

Hereinabove, the present invention is described in derail using theembodiments but not limited to the embodiments described in thisspecification. The scope of the present invention is determined based onthe scope of claims and their equivalents. In the following, adescription is given of modifications obtained by partially modifyingthe aforementioned embodiments.

For example, the thicknesses of the semiconductor light emitting device1 and substrate 2 are just examples and can be properly changed. As anexample, the thickness of the substrate may be set between 1 and 45 μm(preferably, 10 μm or more) so that the total thickness of the device isnot more than 60 μm (preferably, not less than 35 μm and not more than50 μm) in the stacking direction. Moreover, the thickness of the p-typecontact layer in the stacking direction can be changed between 2 and 10μm, for example.

Furthermore, the thickness and materials of each semiconductor layerstacked on the substrate 2 are just examples and can be properlychanged. For example, the light emitting layer may be composed of a GaAsor AlGaAs semiconductor layer or composed of a MQW structure in which aInGaAs semiconductor layer and a GaAs or AlGaAs semiconductor layer arealternately stacked on each other. In the case where the light emittinglayer has such a MQW structure, the number of pairs of well and barrierlayers may be properly changed.

In the method of manufacturing the semiconductor device, the etchingsolution used to etch the substrate 2 can be ammonium, HF, H₂SO₄ typeetching solution.

Moreover, like a semiconductor light emitting device 1B shown in FIG. 9,the electrode-side reflecting layer 8 in the aforementionedsemiconductor light emitting device 1 may be omitted while a p-sideelectrode 9 b is directly formed on the p-type contact layer 7. In sucha structure, the substrate 2 may be increased in thickness by thethickness of the electrode-side reflecting layer 8.

In the aforementioned semiconductor light emitting device 1 (1A), thesubstrate-side reflecting layer 3 (3A) is composed of the two reflectinglayers 3 a and 3 b (3 c and 3 d) but may be composed of a singlereflecting layer. Moreover, the substrate-side reflecting layer 3 (3A)may be omitted.

What is claimed is:
 1. A semiconductor light emitting device comprising:a substrate made of GaAs; and a semiconductor layer formed on thesubstrate, wherein the semiconductor light emitting device has athickness of not more than 60 μm.
 2. The semiconductor light emittingdevice of claim 1, wherein the semiconductor layer contains a firstreflecting layer disposed on the remaining part of the substrate, and asecond reflecting layer disposed on the first reflecting layer and ann-type clad layer disposed on the second reflecting layer, and the firstreflecting layer and the second reflecting layer each having aDistributed Bragg Reflector (DBR) structure that includes a plurality ofstacked layers wherein each layer of the DBR structures has a differentcomposition than a composition of an adjacent layer stacked on therespective layer.
 3. The semiconductor light emitting device of claim 2,wherein the DBR structure of the first reflecting layer includes AlInPlayers and GaAs layers stacked on each other.
 4. The semiconductor lightemitting device of claim 2, wherein the DBR structure of the secondreflecting layer includes AlInP layers and AlGaInP layers stacked oneach other.
 5. The semiconductor light emitting device of claim 3,wherein the semiconductor layer includes a p-type clad layer and anelectrode-side reflecting layer disposed above the p-type clad layer,the electrode-side reflecting layer having a DBR structure whichincludes AlInP layers and AlGaInP layers stacked on each other.
 6. Thesemiconductor light emitting device of claim 5, wherein a p-sideelectrode covers an upper surface and side surfaces of theelectrode-side reflecting layer.
 7. The semiconductor light emittingdevice of claim 2, wherein the DBR structure of the first reflectinglayer includes Al_(y)In_(1-y)P layers (0.3<=y<=0.7) and GaAs layersstacked on each other.
 8. The semiconductor light emitting device ofclaim 7, wherein the DBR structure of the second reflecting layerincludes Al_(y)In_(1-y)P layers (0.3<=y<=0.7) and(Al_(x)Ga_(1-x))_(0.5)In_(0.5)P layers (0.3<=x<=0.85) stacked on eachother.
 9. The semiconductor light emitting device of claim 8, whereinthe semiconductor layer includes a p-type clad layer and anelectrode-side reflecting layer disposed above the p-type clad layer,the electrode-side reflecting layer having a DBR structure whichincludes Al_(y)In_(1-y)P layers (0.3<=y<=0.7) and(Al_(0.3)Ga_(0.7))_(0.6)In_(0.5)P layers stacked on each other.
 10. Thesemiconductor light emitting device of claim 9, wherein a p-sideelectrode covers an upper surface and side surfaces of theelectrode-side reflecting layer.